#define _CRT_SECURE_NO_WARNINGS  1


bool hasCycle(struct ListNode* head)
{
    struct ListNode* fast = head;
    struct ListNode* slow = head;
    while (fast && fast->next)
    {
        fast = fast->next->next;
        slow = slow->next;

        if (fast == slow)
            return true;
    }
    return false;
}